You have to explore it through the doors located in the Grand Chasm. If you follow the arrow when you are in there, it will take you right to the door. After you get through it, it will tell you to talk to Drake and than you will be able to go through the portal.

I think you mean the doors through the Plaza of Conquest. If you go into the Plaza of Conquest, you will see it on the map (at the top).

sanmil0963 wrote:

You have to explore it through the doors located in the Grand Chasm. If you follow the arrow when you are in there, it will take you right to the door. After you get through it, it will tell you to talk to Drake and than you will be able to go through the portal.